Idle Air Control Valve

The Idle Air Control (IAC) valve controls the amount of air that bypasses the throttle valve, which controls the engine idle speed. The IAC valve consists of windings, an armature, a return spring, and a rotary slide. The engine control module (ECM) pulses the voltage to the winding, the opposing forces on the armature by the return spring cause it to maintain a fixed position, adjusting the amount of bypass air to maintain the correct idle speed.